This invention relates generally to devices and methods for delivering a selected medication or other therapeutic fluid to a patient at a subcutaneous infusion site. More particularly, this invention relates to an improved medication infusion set of the type having a soft or flexible cannula adapted for subcutaneous placement, in combination with an infusion needle associated with a protective shroud plate to minimize risk of patient contact therewith while providing a high strength and unidirectional releasible coupling with the cannula.
Medication injection or infusion sets are generally well known in the art, to include a relatively soft and flexible cannula providing a transcutaneous pathway through which a selected medication or other therapeutic fluid can be administered to a patient at a selected subcutaneous site. In a common form, the soft cannula is carried by a compact housing to include a resilient self-sealing septum mounted at an upstream end of the cannula. This cannula housing is initially assembled with an insertion needle extending through the septum and cannula, wherein the insertion needle is manipulated to pierce the patient""s skin to place the cannula transcutaneously, followed by withdrawal of the insertion needle to leave the soft cannula in place on the patient. The selected medication is then coupled to the cannula, typically by means of a length of infusion tubing connected to a medication source, to deliver the medication through the cannula to the patient. In one configuration, the infusion tubing is connected to the cannula housing at a location downstream from the septum as shown, for example, in U.S. Pat. Nos. 4,755,173; 5,176,662; and 5,257,980. In another arrangement, the infusion tubing is coupled to the cannula housing by means of an infusion needle passed through the septum as shown, for example, in U.S. Pat. No. 5,522,803.
Subcutaneous infusion sets of the above-described type are used extensively to administer medication to a patient over an extended period of time. For example, such infusion sets are used with medication infusion pumps of the type described in U.S. Pat. Nos. 4,562,751; 4,685,903; 5,080,653; and 5,097,122 for delivering a long-term medication such as insulin in a continuous or programmable dosage to the patient. With such medication delivery systems, however, it is known that the medication source must be periodically disconnected from the cannula. For example, it has been recognized that the infusion set should be replaced every few days, whereby it is necessary for the patient to uncouple the medication source from an in situ cannula upon removal thereof from the patient, and to recouple the infusion tubing with a second, newly placed cannula. In addition, some patients may briefly disconnect the medication source and related infusion tubing from the cannula to facilitate certain activities, such as swimming or bathing, or participation in certain athletic activities, etc.
In this regard, an optimal medication infusion set is adapted for low profile and in obtrusive placement on the patient, while permitting quick and safe periodic disconnection from and reconnection to the medication source. To this end, use of an infusion needle adapted for coupling through the self-sealing septum provides a quick and easy structure for connecting and disconnecting the medication source from the cannula, but also subjects the patient to undesirable needle sticks from exposure to the infusion needle. Moreover, this arrangement requires a strong and reliable mechanical interlock between the cannula housing and the infusion needle to insure consistent and proper interengagement without inadvertent component separation, while permitting quick and easy and repeated disconnection when desired. All of these features are desirably provided in an infusion set constructed from relatively simple and preferably disposable components which can be manufactured in a cost-efficient manner from medical grade plastic or the like.
The present invention provides an improved medication infusion set designed to meet these features and advantages, by including an infusion needle associated with a protective shroud plate. The shroud plate closely overlies and substantially encases the infusion needle in a manner minimizing risk of patient contact therewith, while additionally providing a strong guide structure for keyed or one-way interconnection with a cannula housing.
In accordance with the invention, an improved medication infusion set is provided for use in delivering medication through a soft cannula to a selected subcutaneous infusion site on a patient. The soft cannula is supported by a compact and low profile cannula housing which includes a self-sealing septum disposed at a proximal or upstream end of the cannula. An infusion hub is provided with latch means for releasible assembly with the cannula housing, and includes a short infusion needle coupled via infusion tubing or the like to a source of the selected medication. The infusion hub includes a protective shroud plate which closely overlies and substantially encases the infusion needle to reduce risk of inadvertent patient contact therewith. The protective shroud plate is configured for unidirectional or one-way reception into a matingly shaped slot formed in the cannula housing upon assembly of the components to provide a high strength connection.
In the preferred form on the invention, the cannula housing comprises a compact plastic molding defining an internal bore for seated reception of a proximal end of the soft cannula. A generally cylindrical needle guide is also seated within the cannula housing and has a downstream end press-fitted into the cannula proximal end. The needle guide defines a flared upstream end, and a ball-shaped resilient and self-sealing septum is retained therein by a retainer clip adapted for snap-fit mounting onto the cannula housing.
The cannula housing is initially assembled with an insertion hub which may also be formed from a molded plastic and includes at least one and preferably a pair of resilient latch arms for snap-fit reception into aligned latch ports formed in a proximal face of the cannula housing. The insertion hub carries an elongated insertion needle passed through the septum and needle guide, and further through the soft cannula terminating in a pointed tip end disposed a short distance beyond the distal or downstream end of the cannula. The insertion needle is utilized to pierce the patient""s skin at a selected medication infusion site, to transcutaneously place the soft cannula, after which the insertion hub is separated from the cannula housing to withdraw the insertion needle from the cannula.
The infusion hub also comprises a low profile component of molded plastic or the like and carries the infusion needle in flow communication with the source of the selected medication, typically via a length of infusion tubing. The infusion needle protrudes from a distal face of the infusion hub in close association with the protective shroud plate which protrudes at least slightly beyond the tip end of the infusion needle. In a preferred form, the shroud plate comprises a multifaceted and preferably three-sided structure enclosing the infusion needle on three sides to substantially prevent patient contact and accidental needle sticks. The shroud plate is configured for slide-fit reception into a matingly shaped slot formed in the proximal face of the cannula housing, with a one-way fit, for accurate guided reception of the infusion needle through the septum to extend partially into the needle guide. At least one and preferably a pair of resilient latch arms on the infusion hub are provided for snap-fit reception into the latch ports on the cannula housing to releasibly interlock the components.
In use, the infusion hub is securely coupled with the cannula housing with a high strength interconnection resistant to bending or twisting forces that could otherwise contribute to inadvertent component separation. However, the infusion hub can be quickly and easily disconnected from the cannula housing when desired, for example, when the cannula is replaced or during patient activities requiring temporary disconnection of the medication source. The infusion hub is adapted for quick and easy reconnection to the existing or to a replacement cannula housing, with a simple one-way snap-fit connection, and with the infusion needle substantially concealed from patient contact at all times.
Other features and advantages of the present invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.